Bump flake8 from 3.5.0 to 3.6.0 in /{{cookiecutter.app_name}}

Bumps [flake8](https://gitlab.com/pycqa/flake8) from 3.5.0 to 3.6.0.
- [Release notes](https://gitlab.com/pycqa/flake8/tags)
- [Commits](https://gitlab.com/pycqa/flake8/compare/3.5.0...3.6.0

)

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